Form



May 16, 1944. c. D. SMITH ET AL FORM Filed 001:. 16 1942 2 Sheets-Sheet 2 INVENTORs.

m 4 w s H d l m Y B May 16,1944 c. D. SMITH ET Al.

FOR'M' Filed Oct 15, 1942 2 Sheets-Sheet 1- INVENTORJ. emu 5 2.5M?! and. 07/10 a: 15 5/11/77! I? THUR/ME Y5.

Patented May 16, 1944 FORM Charles D. Smith and Otho S. F. Smith, Anderson, Ind., assignors to Smaller War Plants Corporation, Chicago, 111., a corporation of the United States Application October 16, 1942, Serial No. 462,238

11 Claims.

In the manufacture of certain hollow bodies having relatively small openings, it is customary to form the body upon a properly shaped core so designed or constructed as to be removable through the opening in the hollow body after the core has served its purpose. Our invention relates to cores of this type, and more particularly to a core suitable for use in the formation of a hollow rubber body. Our invention has for its more important objects the provision of a core which can be cheaply and economically constructed without the use of critical materials, which while light in weight will provide a sufficiently strong and rigid support for the hollow body during those stages of its manufacture in which a support is necessary, which can be readil removed from the interior of the hollow body when its presence therein is no longer necessary, and which will contain a relatively high proportion of parts capable of reuse.

A core made in accordance with our invention conforms to the interior shape of the hollow body in conjunction with the manufacture of which it is to be used. The core itself is hollow, and its walls are preferably formed of light-weight, reasonably rigid sheet material, such as corrugated paper, reinforced and built up where necessary to create the proper shape with some material, such as a papiermach mix, which can be applied and shaped in a plastic state. To strengthen the core, it is desirably provided in teriorly with a system of bracing. The core is formed with an opening in one wall, such opening corresponding in location to the opening in the article to be formed upon the core; and the interior core-bracing is so designed as to be removable through the aligned openings in the walls of the core and the article formed upon it.

The accompanying drawings illustrate my invention: Fig. 1 is a side elevation of a complete core with portions thereof broken away illustrating the interior construction; Fig. 2 is a perspective view illustrating the first step in the formation of the core; Fig. 3 is a plan view, with portions broken away and shown in section, illustrating a subsequent step in the formation of the core; Fig. 4 is a vertical section on the line 4-4 of Fig. 1; Fig. 5 is a fragmental vertical section on an enlarged scale illustrating a detail of construction; Figs. 6 and '7 are fragmental perspective views illustrating different steps in the construction of the core; and Fig. 8 is a diagrammatic view illustrating a modified form of interior bracing.

The complete core illustrated in elevation i Can Fig. 1 and in section in Fig. 4 embodies plane, parallel side walls in and II, convexly curved top and bottom walls I2 and [3 respectively, and plane, approximately parallel end Walls I4 and Hi. In the top wall l2, near the end wall l5, there is a rectangular opening l6 positioned for alignment with the core-removing opening in the completed articlewhich is to be formed on the core. It is to be understood that this particular core is shown merely by way of example and that our invention is not limited to any particular form of core.

In forming the illustrated core by the preferred method, we employ a male form I! (Fig. 2) and a female form l8 (Fig. 3), the interior of the latter conforming, with appropriate allowances for shrinkage or other changes in dimension, to the interior size and shape of the article which the core is to support. The male form I! is of the same general shape, but is smaller in all its dimensions by an extent dependent upon the thickness of the core walls as formed on the form l1.

Where, as in the specific core illustrated in the drawings, the outer surfaces of the core walls are developable, or substantially so, we prefer to form such walls at least in part of corrugated paper. We have found it convenient for this purpose to use so-called double-wall box board which comprises two outer and one intermediate plane sheets separated from each other by corrugated sheets.

With the form l'l resting on any suitable support, we apply sheets of the double-wall box board to the exposed faces of the form, as indicated in Fig. 2. If one side wall of the core is larger than the opposite wall, as is the case in the illustrated core where the side wall l is both wider and longer than the side wall 10, that face of the form I! corresponding to the larger corewall is placed on the bottom; as stripping of the core from the form will thereby be facilitated.-

We find it desirable, for the purpose of increasing stifiness and strength, to so out each sheet that the corrugations therein will extend parallel to the shorter dimension thereof. To unite the several sheets together and to impart to the edges of the core the desired conformation, as well as to stiffen and strengthen the edge portions of the core, we employ a papier-mach mix, desirably first flattening the sheets attheir edges, as by the application of a roller thereto, in the manner indicated at 20 in Figs. 2 and 7. The papier-mach mix 2| is then applied over the flattened edge portions of the sheets, and

smoothed to provide the desired conformation. It may be desirable, before applying the papiermach mix 2|, to tie the edge portions of meeting sheets together as by the use of strips of gummed tape I9 applied at intervals along such edges, as shown in Fig. 2.

In the core shown in the drawings, the corewalls as produced on the form I1 are of substantially uniform thickness, such thickness being that of the box board used. It is to be understood, however, that this is not essential. If the exterior surface of a core of the desired shape contains portions which are not developable,

those portions can be formed with papier-mach mix applied over the sheets of box board to give to the core the desired exterior shape. Where little or none of the exterior surface of the core is developable, it may be desirable to eliminate the box-board or other sheet material altogether and make the core-walls entirely of papiermach mix applied to the exposed surfaces of the male form. However, because of the inherent stiffness and strength of the box board, it is desirable to use it, or an equivalent sheet material, wherever the shape of the core is suitable. added reason for the use of box board or other sheet material in the formation of core-walls having a developable outer surface is found in the fact that with a properly shaped form I1 the proper configuration is imparted to the core wall merely by bringing a sheet of appropriate thickness into engagement with such form.

When the core has dried on the form |'|,'it is stripped therefrom, inverted to bring its open side uppermost, and inserted into the female form I8, as illustrated in Fig. 3'. With the core supported in the form I8, the interior bracing between the top and bottom walls I2 and I3 is applied. As shown in the drawings, such bracing comprises a series of pivotally interconnected struts 22, preferably of wood, each of which is provided with a cross piece 23 at one end and is pivotally connected at the opposite end. to the next preceding strut in the series near the crosspiece 23 thereon. The first strut in the series, designated 22a in the drawings, in addition to being provided with a cross-piece 23 at the end nearest its point of interconnection with the next strut in the series, is provided at its opposite end with a cross-piece 23' adapted to fit'in the angle between the top wall I2 and the end wall I4 remote from the opening I6, as will be clear from Fig. 3.

In applying the bracing, the cross-piece 23 on the end strut 22a is placed in the angle between the top wall I2 and end wall I4 of the core, while the cross-piece 23 at the opposite end of the strut 22a is brought into engagement with the bottom wall I3 of the core. The strut 22a is of such a length that with its ends in the positions just described it will extend obliquely across the core desirably at such an angle that friction between the cross-piece 23 and the bottom wall I3 of the core will tend to retain the strut in place. The next strut 22 is then swung about its point of pivotal connection with the strut 22a until the cross-piece 23% its end engages the top wall I2 of the core, and this operation is repeated with each succeeding strut until all are in place as indicated in Fig. 3.

For the purpose of locating the bracing comprising the struts 22 in the proper plane in the core, we may employ pads 25 illustrated on an enlarged scale in Fig. 5. Each of these pads is conveniently formed of a piece of doublewal1 box board provided centrally with an opening adapted to receive the associated cross-piece 23. The pads 25 may be glued to the inner surfaces of the top and bottom core-walls I2 and I3 to hold them in place.

The series of struts 22 extend to a point adjacent the opening I 6, the last one of such struts desirably having its free end located in contact with the bottom'wall I3 of the core at a point approximately opposite the opening I6. After the struts 22 are all in place, a brace 21 is applied, such brace being provided at one end with a cross-piece 28 adapted to fit within the core at the angle between the top wall I2 and end wall I5, the brace extending obliquely across the interior of the core and intersecting the last strut 22 near the free end thereof. The brace is then secured to such last strut 22, as by means of a removable bolt 29. As will be obvious, the brace 21 serves to hold the last strut 22 in proper position and thus to locate all the struts of the series.

If additional bracing between the top and bottom walls of the core is desired over that extent thereof occupied by the oblique brace 21, an additional strut 30 having cross-pieces 30' at its ends may be employed. Such strut has wallengaging cross-pieces 30' at its ends, extends across the interior of the core in the plane of the bracing comprised by the struts 22, and conveniently is pivotally secured to the brace 21.

While the core is still in the form I8, and either before or after the several struts and the brace 21 havev been placed in position as above described, we glue to the inner surfaces of the core a strip 3|, conveniently of double wall box board, which extends completely around the inside of the core ashort distance from its open side and which will later serve as a seat for the side wall I I when it is put in place.

The bracing so far described acts only between the top and bottom walls I2 and I3 of the core. Bracing between the plane side walls of the core is conveniently provided by the use of hollow cylinders 34 of cardboard or corrugated paper. These cylinders have closed ends or other endwise presented surfaces which are glued to the interior surface of the side core-wall I0 and are distributed over such core-wall between the struts 22 and 30 and the brace 2'! in any suitable pattern, such as is indicated in Fig. 3. The free ends of the cylinders 34 and the outer edge of the strip 3| all lie in substantially the same plane so as to engage the inner surface of the second side wall I I when the latter is applied to the core.

Preferably before the cylinders 34 are glued to the side-wall I0, but not necessarily so, we apply papier-mach mix 35 to the interior of the core at those portions thereof Where strengthening, stiflening, or sealing is desired. Thus, as shown in the drawings, the papier-mach mix may be applied over the entire inner surfaces of the top and bottom walls I2 and I3 and the end walls I4 and I5, generous fillets being provided at the angles where those walls join each other and also where they join the side wall III. In thus applying papier-mach mix, the pads 25 are completely covered (Figs. 3 and 5), as is also the lower edge and inner side surface of the strip 3| (Fig. 6) but, for a reason which will be apparent hereinafter, the outer edge of the strip 3| is not covered with the mix. Sealing of all exposed edges and ends of the walls and other corrugated-paper elements, such as the pads 25, is especially desirable where, in the process of making the article formed upon the core, the interior of the core will be exposed to the action of water, steam, or other substance which would tend to soften the paper. If desired, in order further to moisture-proof the core, it may be-partially or wholly lined with some moisture-repellent sheet material, such as kraft paper (not shown) before the papier-m-ach mix is applied.

In applying the papier-mach mix 35 in the vicinity of the strip 3| we anchor in such mix the edge portions of strips 31 of flexible material desirably kraft-paper, which extend completely around the open side of the core and which are wide enough to project for a considerable distance beyond the edges of the core-walls l2, l3, l4, and 55, as shown in Fig. 3. Desirably,'the papier-mach 35 in the vicinity of the strip 3i is built up on the inside of the core to a point somewhat above the outer edge of the strip 3| as indicated in dotted lines in Fig. 6; so that when the side wall H is put in place within the open end of the core and seated upon the strip 3i this excess papier-mach mix will be displaced, adhering to the under surface of the side wall H adjacent its periphery and thus sealing the edges of the wall H and the upper edge of the strip 3|.

Before the side wall l is put in place. glue is applied to the exposed ends of the cylinders 34 so that the side wall H will adhere thereto. After the side wall i i has been put in place and firmly seated on the strip iii and against the ends of the cylinders 34, tabs 38 formed by a series of spaced transverse cuts in the projecting portion of the strip 31 are folded alternately over and glued to the side Wall H and the adjoinin walls of the core, as will be clear from The edge portion of the core adjacent the edges of the side wall H are then subjected to the mashing action of a roller and subsequently built up with papier-mach mix to the desired conformation, as in the manner indicated in Fig. '7. -It may be desirable to support the upper wall I2 of the core adjacent the edges of the opening it therein; and for this purpose, we may ern ploy the expedient illustrated in the drawings. As there shown. a rigid rectangular frame 40 (Fig. 1) having a central opening approximately corresponding in size and shape to the opening is held in place against the lower surface of the upper core-wall I2, with its opening aligned with the opening H5, by a retaining member 4! which has one end pivoted; to the brace 27 beneath the opening It and whichis provided at its opposite end with a cross piece 42 adapted to engage the frame it and hold it in position. The member M is of such a length and is pivoted to the brace 21 at such a point that the path followed by the cross-piece 42 as it moves from the position illustrated in Fig. 3 to the position illustrated in Fig. 1 approaches tangency with the lower surface of the frame &8, with the re suit that the member 51 will be held firmly place by friction between the cross-piece 42 and the frame Ml.

The cross-piece 42 is long enough to extend across the rectangular opening in the frame 41!] parallel to the smaller dimension of such opening, but is short enough to pass through such opening when rotated into a position parallel to the longer dimension thereof; and the crosspiece 62 is rotatably mounted upon the member 4| so that it can be swung from a position bridgbeing passed through the opening therein.

The core as above described is ready for the application to it of whatever material is to be used in the formation of the desired hollow container. As previously indicated, our core is particularly adapted for the formation of rubber containers, the rubber being applied in sheets wrapped around the core and so arranged as to leave in the top wall of the container an opening corresponding in location to the opening 16 in the top wall l2 of the core. If deemed desirable, application of the frame 4E1 may be deferred and not effected until it is accomplished as an incident in the building up of material on the core. After the desired thickness of rubber has been built up upon the core, the container, with the core inside it, is subjected to any desired curing process, usually the so-called open steam cure in which it is subjected to contact with steam under pressure for a more or less extended period.

Upon termination of the curing process, the body of the hollow container is completed; and upon removal from the curing chamber, the core may be withdrawn. In effecting withdrawal of the core, the operator, by working through the opening it and the aligned opening in the container, swings the member 4| to release the frame 48, which is then withdrawn through the openings. The operator then removes the bolt 29, thus making it possible to move the brace 27, strut 3i and member M toward the center of the core and to swing them into approximate alignment so that, as a unit, they can be withdrawn through the opening it. Swinging of the cross-piece 42 about its pivotal mounting on the end of the member 3? facilitates such with d'rawal. The cross pieces 35! and 28, as well as the cross-pieces 23' and 23, may in most instances be short enough to pass through the opening it without the necessity for rotating them relative to the members upon which they are mounted. Upon removal of the brace 21, strut 3 and member M, the operator reaches through the opening it and tears the lower end of the end strut 22 loose from the bottom wall 13 of the core. By pulling on this end strut after it has been released from the bottom wall, the next succeeding strut 22 is loosened from the top wall; and by repeating this process with each succeeding strut, all of them may successively be torn loose and withdrawn through the opening 16. The papier-mach walls of the core may .den be torn up and removed through the open ing I5 to leave the interior of the completed container unobstructed and free from all coreparts.

In the case of rubber containers completed by a curing process involving their treatment with steam under pressure, the removal of the articles from the curing chamber and their subsequent cooling causes a condensation of steam within the core, the amount of steam condensing usually being sumcient to leave a considerable body of water within the core. This water, supplemented by additional water if desired, aids in the disintegration of the core and thereby facilitates its removal. The cardboard. or corrugated paper cylinders 34 will be softened and rendered more easily subject to tearing by the application of water to them, so that they are easily broken and torn loose when the wooden bracing is removed from the core. Tearing loose of the ends of the struts usually involves some tearing of ing the frame to one in which it is capable of the box-board walls in the vicinity of the pads 25, thus exposing the corrugated paper layers of the box board so that water, entering the channels provided thereby, will reach and soften most portions of the core walls.

' We find that the paper and papier-mach core-walls, especially if wet, tend to separate easily from the interior surfaces of a rubber container without injury to the latter. If desired, however, the finished core may be coatedwith some material which will facilitate its later separation from the inner surfaces of the article formed upon it. Where such article is of rubber, a suitable coating may be provided on the core by application of a water-soluble starch size.

In the core illustrated in Figs. 1 to 4 inclusive, the system of interconnected struts 22 occupies more than half the length of the core. This arrangement is desirable and convenient when the opening I6 is located near one end of the core. However, in other situations, as where the open ing is located near the center of the core, it may be desirable to employ two sets of pivotally interconnected struts 22, each set extending inwardly of the core from one end thereof, as indicated in Fig. 8. In such a situation, the two series of struts are locked in position by a brace 21' extending between points adjacent the free ends of the innermost struts of each set. The connection of the brace 27' to one of uch innermost struts 22 may be a permanent connection, but the other connection is severable, like the connection provided by the bolt 29 in the arrangement of Figs. 1 to 4, so as to permit the bracing to be withdrawn through the opening in the core.

The entire core is made of materials which are both low in price and readily available, so that the manufacture of cores can be carried out on a very economical basis. Moreover, all the interior bracing comprising the struts 22 and 30, brace 21, and member 4!, together with all the crosspieces on the ends of such elements; are capable of repeated reuse, thus further reducing the cost of manufacturing of cores in quantity.

The arrangement in which the struts 22 are shown as pivotally interconnected in Figs. 1 and 3 has an advantage in that a single set of pivotally interconnected struts can be used, within limits, in core of different heights, the angles at which the respective struts are disposed varying to suit the circumstances. Thus, with a core having a vertical dimension somewhat greater than that shown in the drawings, the struts 20 would occupy more nearly vertical positions, the entire series of struts would occupy less of the longitudinal extent of the core, and the only necessary structural change would be an increase in the eifective length of the brace 2'! (or 21').

It will be noted that in the core illustrated and described herein all edge portions of all the various corrugated paper (box board) elements employed are completely covered with papiermache' mix. Along all outer edges of the core, this covering of the edge of the box board walls is effected by the papier-mach mix 2|, while within the core the same purpose is served by the papier-mach lining 35. Thus, moisture is prevented from reaching the edges of, the boxboard where it might enter the channels formed by the corrugated paper and efiect a premature softening and weakening of the core-walls. Where, as at the edges of the opening [6 in the core illustrated in the drawings, it is impracticable or inconvenient to cover and seal exposed edges of box-board with papier-mach mix, those edges may be covered with kraft-paper tape, as-

indicated at IS in Fig. 1. In addition to its function as a means for sealing the edges of the box board, the papier-mach mix acts as a stiffen- .ing and strengthening agent, and may also be used on the exterior of the core to impart the desired conformation thereto.

We claim as our invention:

1. A core for use in the manufacture of hollow articles, said core being hollow and comprising-- side-wall portions of corrugated paper and edge portions of papier-mach, said core being provided interiorly with bracing extending between opposite side-wall-portions, said bracing including a series of pivotally interconnected struts adjacent ones of which extend oppositely obliquely across the core.

2. A core for us in the manufacture of hollow articles, said core being hollow and comprising a pair of opposite side walls which are approximately plane and parallel, a second pair of opposite side walls which are convexly curved, and a pair of end walls, each of said walls being formed of a sheet of corrugated paper, the edge portions of each of said'sheets being flattened and covered exteriorly of the core with papier-mach shaped to predetermined conformation, papier-mach fillets at the interior angles within the core, bracing comprising compression members extending between said curved side walls within the core and additional members within the core ex tending between and secured to said plane side walls.

3. The invention set forth in claim 2 with the addition that said additional members comprise 1 core and positions in which adjacent struts are in approximate alinement with each other.

5. A core for use in the manufacture of hollowarticles, said core being hollow and comprising side-wall portions of corrugated paper, the meeting edges of adjacent side-wall portions being flattened and covered with papier-mach shaped to predetermined conformation.

6. A core for use in the manufacture of hollow articles, said core being hollow and comprising side-wall portions of corrugated paper, the meeting edges of adjacent side-wall portions being flattened and covered with a settable plastic ma terial shaped to predetermined conformation.

'7. A core for use in the manufacture of hollow articles, said core being hollow and comprising side-wall portions of sheet material, the meetin edges of adjacent side-wall portions being covered both interiorly and exteriorly of the core with a settable plastic material shaped to predetermined conformation.

8. A core for use in the manufacture of hollow articles, said core being hollow and comprisin opposite side walls, said core being provided interiorly with bracing extending between said 0pposite side walls, said bracing including a series 10. The invention set forth in claim 8 with the addition that the ends of said struts are secured to said opposite side walls whereby relative movement of the struts will tend to distort said side walls.

11. The invention set forth in claim 9 with the addition that the ends of said struts are secured to said opposite side walls whereby relative movement of the struts will tend to distort said 1 side walls.

CHAS. D. SMITH. OTHO S. F. SMITH. 

